DD âDynamic Dualâ exhaust of the past. Our distinctive DD exhausts with twin high-flow, low restriction compact muffler section, have always been recognized for its aggressive dual exit look and racy sound. With this new high-quality, race-inspired DD-R, we also incorporated updated and improved, full 304 stainless-steel construction and new configurable features. The GPP DD-R has been adapted to modern tuner cars to not only enhances the looks and increase the growl of the engine, but to improve performance with its carefully designed dual high-flow straight-through muffler layouts. The new configurable features on the DD-R include the twin removable tips, with various options for tips finishers and silencers. This now allows the owner to easily fine-tune the looks, sound and flow of their DD-R. GPPâs newest exhaust style is here⊠stay tuned for more updates, and options.